[Bug 2307] line-height: 0 generates parse error

http://www.w3.org/Bugs/Public/show_bug.cgi?id=2307

           Summary: line-height: 0 generates parse error
           Product: CSSValidator
           Version: CSS Validator
          Platform: Macintosh
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: CSS 2.0
        AssignedTo: ot@w3.org
        ReportedBy: akuehn@nc.rr.com
         QAContact: www-validator-cvs@w3.org


A line-height value of 0 without a length unit generates a parse error and a
complaint about an empty string.  Adding any length unit value (e.g. "0em")
cures the error.  Of course, unit values are supposed to be optional.  This
appears to be a very recently-introduced issue (since 9/25/05 or thereabout).